In the fifth rib= Abdomen. (See Note on 2 Samuel 2:23.)
So Joab and Abishai. — Joab here comes forward as the commander of the pursuit without previous mention. He may have accompanied Abishai from Jerusalem, or he may have joined him on the route; but, now, having murdered Amasa, he assumes his old place as commander-in-chief, doubtless with the connivance of his brother.